为什么 python 抛出错误：AttributeError: 'numpy.ndarray' object has no attribute 'append'？

Question

I am trying to run the following code, but python is throwing the error that numpy has no argument 'append' for the line that says: "ids.append(id)"

path = [os.path.join("data", f) for f in os.listdir("data")]
faces = []
ids = []

for image in path :
    img = Image.open(image).convert('L')
    nimg = np.array(img, 'uint8')
    id = int(os.path.split(image)[1].split(".")[1])
    faces.append(nimg)
    ids.append(id)
    ids = np.array(ids)
clf = cv2.face.EigenFaceRecognizer_create()
clf.train(faces, ids)
clf.write("classifier.yml")

Answer 1

You are converting ids into an array after the first iteration. When running it, you should have only one item in the array as is. I would move the line ids = np.array(ids) to outside the for loop. See below:

path = [os.path.join("data", f) for f in os.listdir("data")]
faces = []
ids = []

for image in path :
    img = Image.open(image).convert('L')
    nimg = np.array(img, 'uint8')
    id = int(os.path.split(image)[1].split(".")[1])
    faces.append(nimg)
    ids.append(id)

ids = np.array(ids)
clf = cv2.face.EigenFaceRecognizer_create()
clf.train(faces, ids)
clf.write("classifier.yml")

If you wanted to truly have it be an array, you would have to use the following styled code, but a list should also be fine until the end.

ids = np.array(ids)
ids = np.append(ids, [id])